This rule applies only to leading 0s and not to trailing 0s being able to omit both leading and trailing 0s would cause the address to be ambiguous. One way to shorten IPv6 addresses is to omit leading 0s in any hextet (that is, 16-bit section). RFC 2373 and RFC 5952 provide two helpful rules for reducing the notation involved in the preferred format, which will be discussed next.

Later in this chapter, you will learn a technique that helps in reading and using IPv6 addresses. The following list shows several examples of IPv6 addresses using the longest representation of the preferred form: 0000:0000:0000:0000:0000:0000:0000:0000Īt first glance, these addresses can look overwhelming. For clarity, the term hextet is used throughout this book when referring to individual 16-bit segments. As Figure 4-1 illustrates, each hextet, with its four hexadecimal digits, is equivalent to 16 bits. An IPv6 address consists of eight hextets separated by colons. The unofficial term for a section of four hexadecimal values is a hextet, similar to the term octet used in IPv4 addressing. Colons separate the groups of 4-bit hexadecimal digits. The longest representation of the preferred form includes a total of 32 hexadecimal values. Although IPv6 address can be written in lowercase or uppercase, RFC 5952, A Recommendation for IPv6 Address Text Representation, recommends that IPv6 addresses be represented in lowercase.įigure 4-1 Preferred Form of IPv6 Address The alphanumeric characters used in hexadecimal are not case sensitive therefore, uppercase and lowercase characters are equivalent.

You will see later in this section how to possibly reduce the number of digits required to represent an IPv6 address. Every 4 bits can be represented by a single hexadecimal digit, for a total of 32 hexadecimal values (0 16 through f 16 ). IPv6 addresses are 128 bits in length and written as a string of hexadecimal digits. These addresses are examined more closely in Chapter 5, “Global Unicast Address,” Chapter 6, “Link-Local Unicast Address,” and Chapter 7, “Multicast Addresses.” Representation of IPv6 Addresses Some addresses, such as global unicast, link-local unicast, and multicast addresses, have more significance in IPv6. This chapter examines all the different types of IPv6 addresses in the unicast, multicast, and anycast categories. You will also learn how to represent many IPv6 addresses with fewer digits, using two simple rules. In this chapter, you will become familiar with reading IPv6 addresses. IPv6 includes new address types as well as changes to familiar address types. However, there are many other differences between the two protocol addresses. An IPv4 address is 32 bits and expressed in dotted-decimal notation, whereas an IPv6 address is 128 bits in length and written in hexadecimal. The most obvious and recognizable difference between IPv4 and IPv6 is the IPv6 address.

2 rules of ipv6 compression